Airfoils, cores, and methods of manufacture for forming airfoils having fluidly connected platform cooling circuits

ABSTRACT

Methods for manufacturing airfoils of gas turbine engines are provided. The methods include forming a main body core, the main body core including a feed cavity core portion, the main body core configured to form at least a part of an airfoil including an airfoil body, a platform, and an attachment element, forming a platform circuit core having a platform core extension, wherein the platform circuit core is configured to form a cooling circuit in the platform, wherein at least one of the feed cavity core portion and the platform core extension comprises a notch, assembling the platform circuit core to the main body core such that the platform core extension engages with the feed cavity core portion at the notch, casting an airfoil using the assembled platform circuit core and main body core, and removing a platform core extension element that is formed at the location of the notch.

BACKGROUND

Illustrative embodiments pertain to the art of turbomachinery, andspecifically to turbine rotor components.

Gas turbine engines are rotary-type combustion turbine engines builtaround a power core made up of a compressor, combustor and turbine,arranged in flow series with an upstream inlet and downstream exhaust.The compressor compresses air from the inlet, which is mixed with fuelin the combustor and ignited to generate hot combustion gas. The turbineextracts energy from the expanding combustion gas, and drives thecompressor via a common shaft. Energy is delivered in the form ofrotational energy in the shaft, reactive thrust from the exhaust, orboth.

The individual compressor and turbine sections in each spool aresubdivided into a number of stages, which are formed of alternating rowsof rotor blade and stator vane airfoils. The airfoils are shaped toturn, accelerate and compress the working fluid flow, or to generatelift for conversion to rotational energy in the turbine.

Airfoils may incorporate various cooling cavities located within theairfoil body and located in other features or parts of the airfoil(e.g., platform, attachment elements, etc.). Manufacturing such airfoilsmay be difficult due to various constraints on the processes thereof,and thus airfoil designs may be impacted by the manufacturingconstraints. Thus, improved processes for forming airfoils may beadvantageous.

BRIEF DESCRIPTION

According to some embodiments, methods for manufacturing airfoils of gasturbine engines are provided. The methods include forming a main bodycore, the main body core including a feed cavity core portion, the mainbody core configured to form at least a part of an airfoil including anairfoil body, a platform, and an attachment element, forming a platformcircuit core having a platform core extension, wherein the platformcircuit core is configured to form a cooling circuit in the platform,wherein at least one of the feed cavity core portion and the platformcore extension comprises a notch, assembling the platform circuit coreto the main body core such that the platform core extension engages withthe feed cavity core portion at the notch, casting an airfoil using theassembled platform circuit core and main body core, and removing aplatform core extension element that is formed at the location of thenotch.

In addition to one or more of the features described above, or as analternative, further embodiments of the methods may include that a gapis formed between the platform core extension and the feed cavity coreportion when engaged.

In addition to one or more of the features described above, or as analternative, further embodiments of the methods may include that theplatform core extension element is formed by material of the castinglocated within the gap.

In addition to one or more of the features described above, or as analternative, further embodiments of the methods may include that the gapis between 0.015 inches and 0.050 inches.

In addition to one or more of the features described above, or as analternative, further embodiments of the methods may include that theremoval of the platform core extension element comprises a machiningprocess.

In addition to one or more of the features described above, or as analternative, further embodiments of the methods may include that removalof the platform core extension element fluidly connects a formed mainbody feed cavity and a formed platform cooling circuit.

In addition to one or more of the features described above, or as analternative, further embodiments of the methods may include that thenotch is formed in the feed cavity core portion and the platform coreextension engages within the notch of the feed cavity core portion.

In addition to one or more of the features described above, or as analternative, further embodiments of the methods may include that thenotch is formed within the platform core extension and the feed cavitycore portion engages within the notch of the platform core extension.

In addition to one or more of the features described above, or as analternative, further embodiments of the methods may include that thefeed cavity core portion comprises a reduced width portion that engageswith the notch of the platform core extension.

According to some embodiments, core assemblies for forming airfoils ofgas turbine engines are provided. The core assemblies include a mainbody core, the main body core including at least one feed cavity coreportion, the main body core configured to form an airfoil including anairfoil body, a platform, and an attachment element and a platformcircuit core having a platform core extension, wherein at least one ofthe feed cavity core portion and the platform core extension comprises anotch. The platform circuit core extension is engageable with the feedcavity core portion at the notch and a gap is formed between theplatform circuit core extension and a surface of the feed cavity coreportion at the notch.

In addition to one or more of the features described above, or as analternative, further embodiments of the core assemblies may include thatthe gap is between 0.015 inches and 0.050 inches.

In addition to one or more of the features described above, or as analternative, further embodiments of the core assemblies may include thatthe notch is formed in the feed cavity core portion and the platformcore extension engages within the notch of the feed cavity core portion.

In addition to one or more of the features described above, or as analternative, further embodiments of the core assemblies may include thatthe notch is formed within the platform core extension and the feedcavity core portion engages within the notch of the platform coreextension.

In addition to one or more of the features described above, or as analternative, further embodiments of the core assemblies may include thatthe feed cavity core portion comprises a reduced width portion thatengages with the notch of the platform core extension.

According to some embodiments, airfoils of gas turbine engines areprovided. The airfoils include an airfoil body extending from a platformand an attachment element, wherein at least one of the platform and theattachment element include at least one feed cavity and a platformcooling circuit formed within the platform, wherein the platform coolingcircuit is fluidly connected to the at least one feed cavity at aplatform cooling circuit bypass.

In addition to one or more of the features described above, or as analternative, further embodiments of the airfoils may include that theplatform cooling circuit comprises at least one platform cooling holeformed in the platform such that cooling air flows from the at least onefeed cavity, through the platform cooling circuit bypass, through theplatform cooling circuit, and out through the at least one platformcooling hole.

In addition to one or more of the features described above, or as analternative, further embodiments of the airfoils may include that theairfoil body defines at least one main body cavity, wherein the mainbody cavity is fluidly connected to the at least one feed cavity.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be understood, however, the following descriptionand drawings are intended to be illustrative and explanatory in natureand non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike: The subject matter is particularly pointed out and distinctlyclaimed at the conclusion of the specification. The foregoing and otherfeatures, and advantages of the present disclosure are apparent from thefollowing detailed description taken in conjunction with theaccompanying drawings in which like elements may be numbered alike and:

FIG. 1 is a schematic cross-sectional illustration of a gas turbineengine;

FIG. 2 is a schematic illustration of a portion of a turbine section ofthe gas turbine engine of FIG. 1;

FIG. 3A is a perspective view of an airfoil that can incorporateembodiments of the present disclosure, as viewing a leading edgethereof;

FIG. 3B is a partial cross-sectional view of the airfoil of FIG. 3A asviewed along the line B-B shown in FIG. 3A;

FIG. 3C is a perspective view of the airfoil of FIG. 3A, as viewing atrailing edge thereof;

FIG. 4A is a partial cutaway, schematic illustration of an airfoilformed in accordance with an embodiment of the present disclosure, aftercasting, but prior to a machining process;

FIG. 4B is a schematic illustration of the airfoil of FIG. 4A after amachining process in accordance with an embodiment of the presentdisclosure;

FIG. 5A is an isometric illustration of an airfoil in accordance with anembodiment of the present disclosure;

FIG. 5B is a sectional of the airfoil of FIG. 5A as viewed at the lineB-B;

FIG. 5C is a sectional of the airfoil of FIG. 5A as viewed at the lineC-C;

FIG. 5D is a sectional of the airfoil of FIG. 5A as viewed at the lineD-D;

FIG. 5E is a sectional of the airfoil of FIG. 5A as viewed at the lineE-E prior to a machining process of the present disclosure;

FIG. 5F is a sectional of the airfoil of FIG. 5A as viewed at the lineE-E after a machining process of the present disclosure;

FIG. 6 is a schematic illustration of a core assembly in accordance withan embodiment of the present disclosure;

FIG. 7 is a flow process for manufacturing an airfoil in accordance withan embodiment of the present disclosure;

FIG. 8 is a schematic illustration of a core assembly in accordance withan embodiment of the present disclosure;

FIG. 9A is a partial-sectional view of an airfoil in accordance with anembodiment of the present disclosure prior to a machining process;

FIG. 9B is a partial-sectional view of the airfoil of FIG. 9A after amachining process in accordance with an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Detailed descriptions of one or more embodiments of the disclosedapparatus and/or methods are presented herein by way of exemplificationand not limitation with reference to the Figures.

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. The fan section 22 drivesair along a bypass flow path B in a bypass duct, while the compressorsection 24 drives air along a core flow path C for compression andcommunication into the combustor section 26 then expansion through theturbine section 28. Although depicted as a two-spool turbofan gasturbine engine in the disclosed non-limiting embodiment, it should beunderstood that the concepts described herein are not limited to usewith two-spool turbofans as the teachings may be applied to other typesof turbine engines.

The exemplary engine 20 generally includes a low speed spool 30 and ahigh speed spool 32 mounted for rotation about an engine centrallongitudinal axis A relative to an engine static structure 36 viaseveral bearing systems 38. It should be understood that various bearingsystems 38 at various locations may alternatively or additionally beprovided, and the location of bearing systems 38 may be varied asappropriate to the application.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a low pressure compressor 44 and a low pressureturbine 46. The inner shaft 40 can be connected to the fan 42 through aspeed change mechanism, which in exemplary gas turbine engine 20 isillustrated as a gear system 48 to drive the fan 42 at a lower speedthan the low speed spool 30. The high speed spool 32 includes an outershaft 50 that interconnects a high pressure compressor 52 and highpressure turbine 54. A combustor 56 is arranged in exemplary gas turbine20 between the high pressure compressor 52 and the high pressure turbine54. An engine static structure 36 is arranged generally between the highpressure turbine 54 and the low pressure turbine 46. The engine staticstructure 36 further supports bearing systems 38 in the turbine section28. The inner shaft 40 and the outer shaft 50 are concentric and rotatevia bearing systems 38 about the engine central longitudinal axis Awhich is collinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The turbines 46, 54 rotationally drive therespective low speed spool 30 and high speed spool 32 in response to theexpansion. It will be appreciated that each of the positions of the fansection 22, compressor section 24, combustor section 26, turbine section28, and fan drive gear system 48 may be varied. For example, gear system48 may be located aft of combustor section 26 or even aft of turbinesection 28, and fan section 22 may be positioned forward or aft of thelocation of gear system 48.

The engine 20 in one example is a high-bypass geared aircraft engine. Ina further example, the engine 20 bypass ratio is greater than about six(6), with an example embodiment being greater than about ten (10), thegear system 48 is an epicyclic gear train, such as a planetary gearsystem or other gear system, with a gear reduction ratio of greater thanabout 2.3 and the low pressure turbine 46 has a pressure ratio that isgreater than about five. In one disclosed embodiment, the engine 20bypass ratio is greater than about ten (10:1), the fan diameter issignificantly larger than that of the low pressure compressor 44, andthe low pressure turbine 46 has a pressure ratio that is greater thanabout five 5:1. Low pressure turbine 46 pressure ratio is pressuremeasured prior to inlet of low pressure turbine 46 as related to thepressure at the outlet of the low pressure turbine 46 prior to anexhaust nozzle. The gear system 48 may be an epicycle gear train, suchas a planetary gear system or other gear system, with a gear reductionratio of greater than about 2.3:1. It should be understood, however,that the above parameters are only exemplary of one embodiment of ageared architecture engine and that the present disclosure is applicableto other gas turbine engines including direct drive turbofans.

A significant amount of thrust is provided by the bypass flow B due tothe high bypass ratio. The fan section 22 of the engine 20 is designedfor a particular flight condition—typically cruise at about 0.8 Mach andabout 35,000 feet (10,688 meters). The flight condition of 0.8 Mach and35,000 ft (10,688 meters), with the engine at its best fuelconsumption—also known as “bucket cruise Thrust Specific FuelConsumption (‘TSFC’)”—is the industry standard parameter of lbm of fuelbeing burned divided by 1 bf of thrust the engine produces at thatminimum point. “Low fan pressure ratio” is the pressure ratio across thefan blade alone, without a Fan Exit Guide Vane (“FEGV”) system. The lowfan pressure ratio as disclosed herein according to one non-limitingembodiment is less than about 1.45. “Low corrected fan tip speed” is theactual fan tip speed in ft/sec divided by an industry standardtemperature correction of [(Tram° R)/(514.7° R)]^(0.5). The “Lowcorrected fan tip speed” as disclosed herein according to onenon-limiting embodiment is less than about 1150 ft/second (350.5 m/sec).

Although the gas turbine engine 20 is depicted as a turbofan, it shouldbe understood that the concepts described herein are not limited to usewith the described configuration, as the teachings may be applied toother types of engines such as, but not limited to, turbojets,turboshafts, and turbofans wherein an intermediate spool includes anintermediate pressure compressor (“IPC”) between a low pressurecompressor (“LPC”) and a high pressure compressor (“HPC”), and anintermediate pressure turbine (“IPT”) between the high pressure turbine(“HPT”) and the low pressure turbine (“LPT”).

FIG. 2 is a schematic view of a turbine section that may employ variousembodiments disclosed herein. Turbine 200 includes a plurality ofairfoils, including, for example, one or more blades 201 and vanes 202(collectively “airfoils 201, 202”). The airfoils 201, 202 may be hollowbodies with internal cavities defining a number of channels or cavities,hereinafter airfoil cavities, formed therein and extending from an innerdiameter 206 to an outer diameter 208, or vice-versa. The airfoilcavities may be separated by partitions or internal walls or structureswithin the airfoils 201, 202 that may extend either from the innerdiameter 206 or the outer diameter 208 of the airfoil 201, 202, or aspartial sections therebetween. The partitions may extend for a portionof the length of the airfoil 201, 202, but may stop or end prior toforming a complete wall within the airfoil 201, 202. Multiple of theairfoil cavities may be fluidly connected and form a fluid path withinthe respective airfoil 201, 202. The blades 201 and the vanes 202, asshown, are airfoils that extend from platforms 210 located proximal tothe inner diameter thereof. Located below the platforms 210 may beairflow ports and/or bleed orifices that enable air to bleed from theinternal cavities of the airfoils 201, 202. A root of the airfoil mayconnect to or be part of the platform 210. Such roots may enableconnection to a turbine disc, as will be appreciated by those of skillin the art.

The turbine 200 is housed within a case 212, which may have multipleparts (e.g., turbine case, diffuser case, etc.). In various locations,components, such as seals, may be positioned between the airfoils 201,202 and the case 212. For example, as shown in FIG. 2, blade outer airseals 214 (hereafter “BOAS”) are located radially outward from theblades 201. As will be appreciated by those of skill in the art, theBOAS 214 can include BOAS supports that are configured to fixedlyconnect or attach the BOAS 214 to the case 212 (e.g., the BOAS supportscan be located between the BOAS and the case). As shown in FIG. 2, thecase 212 includes a plurality of hooks 218 that engage with the hooks216 to secure the BOAS 214 between the case 212 and a tip of the blade201.

As shown and labeled in FIG. 2, a radial direction R is upward on thepage (e.g., radial with respect to an engine axis) and an axialdirection A is to the right on the page (e.g., along an engine axis).Thus, radial cooling flows will travel up or down on the page and axialflows will travel left-to-right (or vice versa). A circumferentialdirection C is a direction into and out of the page about the engineaxis.

Typically, airfoil cooling includes impingement cavities for coolingvarious hot surfaces of the airfoils. For example, it may be desirableto position a leading edge impingement cavity immediately adjacent tothe external leading edge of the airfoil (e.g., left side edge of theairfoils 201, 202). The leading edge impingement cavity is typicallysupplied cooling airflow from impingement apertures which serve asconduits for cooling air that originates within the leading edge coolingcavities of the airfoil. Once in the leading edge impingement cavity,the cooling air flow is expelled through an array of shower head holes,thus providing increased convective cooling and a protective film tomitigate the locally high external heat flux along the leading edgeairfoil surface.

Turning now to FIGS. 3A-3C, schematic illustrations of an airfoil 300are shown. FIG. 3A is an isometric illustration of a leading edge of theairfoil 300. FIG. 3B is a cross-sectional illustration of the airfoil300 as viewed along the line B-B shown in FIG. 3A. FIG. 3C is anisometric illustration of a trailing edge of the airfoil 300. Theairfoil 300, as shown, is arranged as a blade having an airfoil body 302that extends from a platform 304 from a root 306 to a tip 308. Theplatform 304 may be integrally formed with or attached to an attachmentelement 310, the attachment element 310 being configured to attach to orengage with a rotor disc for installation of the airfoil body 302thereto. The airfoil body 302 extends in an axial direction A from aleading edge 312 to a trailing edge 314, and in a radial direction Rfrom the root 306 to the tip 308. In the circumferential direction C,the airfoil body 302 extends between a pressure side 316 and a suctionside 318.

As shown in FIG. 3B, illustrating a cross-sectional view of the airfoil300, as viewed along the line B-B shown in FIG. 3A, the airfoil body 302defines or includes a plurality of internal cavities to enable coolingof the airfoil 300. For example, as shown, the airfoil 300 includes aplurality of forward and side cooling cavities 320, 322, 324. A leadingedge cavity 320 is located along the leading edge 312 of the airfoilbody 302, pressure side cavities 322 are arranged along the pressureside 316 and proximate the leading edge 312, and a suction side cavity324 is arranged along the suction side 318 and proximate the leadingedge 312. In the relative middle of the airfoil body 302, the airfoil300 includes various main body cavities 326, 328, 330, 332 and, at thetrailing edge 314, a trailing edge slot 334. Some of the main bodycavities may form a serpentine flow path through the airfoil 300, (e.g.,cavities 328, 330, 332). Further, one or more of the main body cavitiesmay be arranged to provide cool impinging air into the forward and sidecooling cavities 320, 322, 324 (e.g., cavity 326). In some embodimentsdescribed herein, the cavity 326 may be referred to as a leading edgefeed cavity. Although shown with a specific internal cooling cavityarrangement, airfoils in accordance with the present disclosure mayinclude additional and/or alternative cavities, flow paths, channels,etc. as will be appreciated by those of skill in the art, including, butnot limited to, tip cavities, serpentine cavities, trailing edgecavities, etc.

Some or all of the internal cavities 320, 322, 324, 326, 328, 330, 332may be fed by a cool air supply located within the attachment element310 and through the platform 304. Cooling is also provided to theplatform 304, and particularly to the hot gaspath surfaces of theplatform 304, as will be appreciated by those of skill in the art. Forexample, as shown in FIG. 3C, the platform 304 may include one or moreplatform cooling holes 336. The platform cooling holes 336 may bearranged as film cooling holes that expel cool air from within theplatform 304 out onto a hot gaspath surface. Further, in someembodiments, as will be appreciated by those of skill in the art, theplatform 304 may include one or more platform cooling holes that arearranged on side facing surfaces, e.g., between adjacent blades. Theplatform cooling holes 336 may be fed from a cool air source within orbelow the platform 304 and/or the attachment element 310.

Providing a common cooling source for both the airfoil cavities and theplatform may be difficult due to limitations of manufacturing processes.For example, a core for forming a platform cooling circuit may havedifferent thermal expansion characteristics than a core for forming amain body of an airfoil, and thus during the manufacturing process,consistent and/or efficient means for forming a complete airfoil andplatform may be difficult to achieve. Accordingly, embodiments providedherein are directed to core assemblies and airfoils that enable improvedmanufacturing techniques and improved cooling schemes for airfoils andplatforms of airfoils.

Turning now to FIGS. 4A-4B, schematic illustrations of an airfoil 400 inaccordance with an embodiment of the present disclosure are shown. FIG.4A illustrates a formed airfoil 400 after casting, but prior to amachining process in accordance with the present disclosure, and FIG. 4Billustrates the airfoil 400 after the machining process.

The airfoil 400 is substantially similar to the airfoil 300 shown anddescribed with respect to FIG. 3. As such, the airfoil 400 is arrangedas a blade having an airfoil body 402 that extends from a platform 404from a root 406 to a tip 408. The platform 404 may be integrally formedwith or attached to an attachment element 410, the attachment element410 being configured to attach to or engage with a rotor disc forinstallation of the airfoil body 402 thereto. The airfoil body 402extends in an axial direction from a leading edge 412 to a trailing edge414, and in a radial direction from the root 406 to the tip 408. In acircumferential direction, the airfoil body 402 extends between apressure side (not shown in this view) and a suction side 418. Theplatform 404 includes one or more platform cooling holes 436, asdescribed above.

FIGS. 4A-4B are partial cut-away views, illustrating an internalstructure of a portion of the airfoil body 402, the platform 404, andthe attachment element 410. As shown, the attachment element 410includes at least one main body feed cavity 438 that is arranged tosupply cooling air into the airfoil body 402, e.g., into one or moremain body cavities 440. For example, the main body cavities 440 mayinclude, but are not limited to, one or more of the internal cavities320, 322, 324, 326, 328, 330, 332 shown in FIG. 3B. Also shown is aplatform cooling circuit 442 that can supply cooling air into andthrough the platform 404 and out through the one or more platformcooling holes 436.

In the interim manufacturing step shown in FIG. 4A, the airfoil 400 isformed with a platform core extension element 444. The platform coreextension element 444 is formed during the manufacturing process of thepresent disclosure to enable and/or ensure proper mating and formationof cores.

As shown in FIG. 4B, a machining process may be used to remove theplatform core extension element 444. With the platform core extensionelement 444 removed, the main body feed cavity 438 can now supplycooling air to both the main body cavities 440 and the platform coolingcircuit 442. That is, with the removal of the platform core extensionelement 444, a platform cooling circuit bypass 446 is formed along themain body feed cavity 438 to bleed or extract a portion of the coolingair and divert it into and through the platform cooling circuit 442. Thecooling air will then be expelled out through the one or more platformcooling holes 436.

Turning now to FIGS. 5A-5F, schematic illustrations of an airfoil 500 inaccordance with an embodiment of the present disclosure are shown. FIG.5A is an isometric illustration of the airfoil 500 as viewed toward thetrailing edge thereof, FIG. 5B is a sectional of the airfoil 500 at theline B-B, FIG. 5C is a sectional of the airfoil 500 at the line C-C,FIG. 5D is a sectional of the airfoil 500 at the line D-D, FIG. 5E is asectional of the airfoil 500 at the line E-E, and FIG. 5F is a sectionalof the airfoil 500 at the line E-E after a machining process of thepresent disclosure.

The airfoil 500 is substantially similar to the airfoils shown anddescribed above. The airfoil 500 is arranged as a blade having anairfoil body 502 that extends from a platform 504 extending between aroot and a tip. The platform 504 may be integrally formed with orattached to an attachment element 510, the attachment element 510 beingconfigured to attach to or engage with a rotor disc for installation ofthe airfoil body 502 thereto. The airfoil body 502 extends in an axialdirection between a leading edge and a trailing edge, and in a radialdirection from the root to the tip. In a circumferential direction, theairfoil body extends between a pressure side and a suction side. Theplatform 504 includes one or more platform cooling holes 536, asdescribed above, that fluidly connect to a platform cooling circuit. Theairfoil contains one or more internal main body cavities therein

With reference to FIG. 5B, the sectional illustrates the platform 504with a plurality of main body cavities 540 and a platform coolingcircuit 542 formed therein. The platform cooling circuit 542 includesone or more platform cooling holes 536, as described above and as willbe appreciated by those of skill in the art. As shown in FIG. 5B, theplatform cooling circuit 542 and the main body cavities 540 areseparated. As the platform cooling circuit 542 and the main bodycavities 540 extend radially inward through the attachment element 510,the geometries thereof change, as shown in FIGS. 5C-5D.

Referring now to FIG. 5E, main body feed cavities 538 are shown whichfluidly connected to the main body cavities 540. The main body feedcavities 538 may continue radially inward to a source of cooling airwhen installed within a turbine section of a gas turbine engine. FIG. 5Eillustrates the attachment element 510 pre-machining, but post-casting.That is, a platform core extension element 444 separates the platformcooling circuit 542 from one of the main body feed cavities 538.

As shown in FIG. 5F, which illustrates the same sectional as FIG. 5E,the platform core extension element 544 has been removed, such as bymachining, and the platform cooling circuit 542 is now fluidly connectedto one of the main body feed cavities 538 through a platform coolingcircuit bypass 546. Advantageously, in accordance with embodiments ofthe present disclosure, a single cooling source can be used to supplycooling air to both the main body cavities 540 of an airfoil and also tothe platform cooling circuit 542.

Turning now to FIG. 6, a schematic illustration of a core assembly 650in accordance with an embodiment of the present disclosure is shown. Thecore assembly 650 may be used to form an airfoil in accordance with thepresent disclosure, such as the airfoils shown and described above.

The core assembly includes a main body core 652 and a platform circuitcore 654. The main body core 652 includes an airfoil cavity core portion656 and a feed cavity core portion 658. The airfoil cavity core portion656 can include one or more cores that are arranged and positioned toenable the formation of one or more cavities within a formed airfoilbody. The feed cavity core portion 658 is arranged to aid in theformation of a platform and attachment element and form feed cavitiestherein and/or therethrough. The platform circuit core 654 is arrangedto form a platform cooling circuit within a platform of the formedairfoil, and can include various features as will be appreciated bythose of skill in the art (e.g., features to form one or more platformcooling holes).

As shown, the platform circuit core 654 includes a platform coreextension 660. The platform core extension 660 is arranged to fit withina notch 662 of the feed cavity core portion 658 of the main body core652. That is, the feed cavity core portion 658 of the main body core 652is formed with the notch 662 therein, with the notch 662 positioned toform platform cooling circuit bypass in a formed airfoil.

The dimensions of the platform core extension 660 and the notch 662 areselected to allow for a gap 664 to be present when the platform coreextension 660 is inserted into the notch 662 when casting an airfoil.The gap 664 allows for different thermal expansion coefficients of theplatform circuit core 654 and the main body core 652 during the castingprocess. Thus, failure and/or damage may be avoided during the formationof the airfoil at the location of the joining of the platform circuitcore 654 and the main body core 652. The gap 664 allows for some amountof casting material to enter therein, thus forming a platform coreextension element (e.g., as shown in FIGS. 4A and 5E) which may besubsequently removed by machining or other process, as will beappreciated by those of skill in the art. In accordance with an exampleembodiment, the gap is between about 0.015 inches and about 0.050inches.

Although the platform core extension 660 in FIG. 6 is shown with asubstantially squared cross-section, such geometry is not to belimiting. For example, a cylindrical or conical shape may be employedwithout departing from the scope of the present disclosure. Thegeometric shape of the platform core extension may be arranged toachieve specific design considerations or may be selected for otherreasons. For example, a conical shape may result in a more smoothtransition in the formed cooling cavities (e.g., decreased inletlosses). Other geometries may provide for improved structure, such asovals, smooth, filleted shapes, etc. Accordingly, the geometry of theconnection and engagement at the notch is not to be limiting.

Further, the shape of the formed opening, by removal of the platformcore extension element, may take any desired geometric shapes, and maybe defined, in part, by the shape of the notch and the extension thatengages therewith. Moreover, the machining process may be selected orperformed to achieve a desired transition at the junction between themain body feed cavity and the platform cooling circuit. Thus, theillustrative embodiments shown and described herein are merely forexample and are not to be limiting.

Turning now to FIG. 7, a flow process 700 for forming an airfoil inaccordance with an embodiment of the present disclosure is shown. Theflow process may be used to form an airfoil having a platform coolingcircuit that is fluidly connected to a main body feed cavity, as shownand described above.

At block 702, a main body core is formed, with the main body core beingconfigured to enable casting of an airfoil body having internal cavitiesand main body feed cavities formed within and/or through a platform andan attachment element of the airfoil. At least one feed cavity coreportion of the main body core is formed with a notch, such as shown anddescribed above.

At block 704, a platform circuit core is formed for forming a platformcooling circuit within the platform of the formed airfoil. The platformcircuit core is formed with a platform core extension to enableengagement and assembly with the main body core.

At block 706, the platform circuit core is assembled to the main bodycore with the platform core extension inserted in or engaged with thenotch of the notch of the main body core. When assembled, a gap isformed between the platform core extension and the surfaces of the mainbody core defining the notch. The gap is provided to allow for changesin shape/size of the main body core and/or the platform core extensiondue to thermal influences during a casting process.

At block 708, an airfoil is cast using the assembled platform circuitcore and main body core. During the casting process, a platform coreextension element is formed within the gap between the platform coreextension and the surfaces of the main body core defining the notch.

At block 710, the platform core extension element is removed to form aplatform cooling circuit bypass. That is, the platform core extensionelement is removed to fluidly connect a main body feed cavity to aformed platform cooling circuit.

Turning now to FIG. 8, a schematic illustration of a core assembly 870in accordance with an embodiment of the present disclosure is shown. Thecore assembly 870 may be used to form airfoils having features as shownand described above. In this arrangement, the core assembly 870 includesa platform circuit core 871 and a main body core 872. The platformcircuit core 871 includes a platform core extension 873 defining a notch874 to receive a portion 875 of the main body core 872 therein. The endresult of such configuration is an airfoil similar to that shown anddescribed above. A gap may be present between the notch 874 and theportion 875 of the main body core 872, as described above. As shown, theportion 875 of the main body core 872 may be a reduced thickness portionof the main body core 872 such that the resulting joined main body core872 and platform circuit core 871 do not occupy additional space orvolume as compared to the embodiments shown and described above.

It is noted that FIG. 8 illustrates an alternative configuration to theprior described embodiments. Those of skill in the art will appreciatethat further arrangements may be possible without departing from thescope of the present disclosure. For example, in some embodiments, theplatform circuit core may define a notch at an end thereof, with a coreextension extending from a side of the main body core (i.e., theopposite of the arrangement shown in FIG. 6).

Turning now to FIGS. 9A-9B, schematic illustrations of an airfoil 980 inaccordance with an embodiment of the present disclosure are shown. FIG.9A is a partial-sectional view of the airfoil 980, prior to a machiningprocess. FIG. 9B is a partial-sectional view of the airfoil 980, after amachining process. The airfoil 980 may be formed using a core assemblysimilar to that shown in FIG. 8. The illustration in FIGS. 9A-9B may beof a portion of an attachment element of the airfoil 980, similar tothat shown and described above.

As shown, a main body feed cavity 981 is formed within the airfoil 980and my fluidly connect to one or more main body cavities of the airfoil980. The main body feed cavity 981 may extend, downward on the page, toa source of cooling air when installed within a turbine section of a gasturbine engine. FIG. 9A illustrates the airfoil 980 pre-machining, butpost-casting. In this illustration, a platform core extension element982 separates a platform cooling circuit 983 from the main body feedcavity 981.

FIG. 9B illustrates the same sectional as FIG. 9A, but the platform coreextension element 982 has been removed, such as by machining, and theplatform cooling circuit 983 is now fluidly connected to the main bodyfeed cavity 981 through a platform cooling circuit bypass 984.Advantageously, in accordance with embodiments of the presentdisclosure, a single cooling source can be used to supply cooling air toboth the main body cavities of an airfoil and also to the platformcooling circuit 983.

As used herein, the term “about” is intended to include the degree oferror associated with measurement of the particular quantity based uponthe equipment available at the time of filing the application. Forexample, “about” may include a range of ±8%, or 5%, or 2% of a givenvalue or other percentage change as will be appreciated by those ofskill in the art for the particular measurement and/or dimensionsreferred to herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a,” “an,” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,element components, and/or groups thereof. It should be appreciated thatrelative positional terms such as “forward,” “aft,” “upper,” “lower,”“above,” “below,” “radial,” “axial,” “circumferential,” and the like arewith reference to normal operational attitude and should not beconsidered otherwise limiting.

While the present disclosure has been described with reference to anillustrative embodiment or embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe present disclosure. In addition, many modifications may be made toadapt a particular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof.Therefore, it is intended that the present disclosure not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this present disclosure, but that the present disclosurewill include all embodiments falling within the scope of the claims.

What is claimed is:
 1. A method for manufacturing an airfoil of a gasturbine engine, the method comprising: forming a main body core, themain body core including a feed cavity core portion, the main body coreconfigured to form at least a part of an airfoil including an airfoilbody, a platform, and an attachment element; forming a platform circuitcore having a platform core extension, wherein the platform circuit coreis configured to form a cooling circuit in the platform, wherein atleast one of the feed cavity core portion and the platform coreextension comprises a notch; assembling the platform circuit core to themain body core such that the platform core extension engages with thefeed cavity core portion at the notch; casting an airfoil using theassembled platform circuit core and main body core; and removing aplatform core extension element that is formed at the location of thenotch.
 2. The method of claim 1, wherein a gap is formed between theplatform core extension and the feed cavity core portion when engaged.3. The method of claim 2, wherein the platform core extension element isformed by material of the casting located within the gap.
 4. The methodof claim 2, wherein the gap is between 0.015 inches and 0.050 inches. 5.The method of claim 1, wherein the removal of the platform coreextension element comprises a machining process.
 6. The method of claim1, wherein removal of the platform core extension element fluidlyconnects a formed main body feed cavity and a formed platform coolingcircuit.
 7. The method of claim 1, wherein the notch is formed in thefeed cavity core portion and the platform core extension engages withinthe notch of the feed cavity core portion.
 8. The method of claim 1,wherein the notch is formed within the platform core extension and thefeed cavity core portion engages within the notch of the platform coreextension.
 9. The method of claim 8, wherein the feed cavity coreportion comprises a reduced width portion that engages with the notch ofthe platform core extension.
 10. A core assembly for forming an airfoilof a gas turbine engine, the core assembly comprising: a main body core,the main body core including at least one feed cavity core portion, themain body core configured to form an airfoil including an airfoil body,a platform, and an attachment element; and a platform circuit corehaving a platform core extension, wherein at least one of the feedcavity core portion and the platform core extension comprises a notch;wherein the platform circuit core extension is engageable with the feedcavity core portion at the notch and a gap is formed between theplatform circuit core extension and a surface of the feed cavity coreportion at the notch.
 11. The core assembly of claim 10, wherein the gapis between 0.015 inches and 0.050 inches.
 12. The core assembly of claim10, wherein the notch is formed in the feed cavity core portion and theplatform core extension engages within the notch of the feed cavity coreportion.
 13. The core assembly of claim 10, wherein the notch is formedwithin the platform core extension and the feed cavity core portionengages within the notch of the platform core extension.
 14. The coreassembly of claim 13, wherein the feed cavity core portion comprises areduced width portion that engages with the notch of the platform coreextension.
 15. An airfoil of a gas turbine engine comprising: an airfoilbody extending from a platform and an attachment element, wherein atleast one of the platform and the attachment element include at leastone feed cavity; and a platform cooling circuit formed within theplatform, wherein the platform cooling circuit is fluidly connected tothe at least one feed cavity at a platform cooling circuit bypass. 16.The airfoil of claim 15, wherein the platform cooling circuit comprisesat least one platform cooling hole formed in the platform such thatcooling air flows from the at least one feed cavity, through theplatform cooling circuit bypass, through the platform cooling circuit,and out through the at least one platform cooling hole.
 17. The airfoilof claim 15, wherein the airfoil body defines at least one main bodycavity, wherein the main body cavity is fluidly connected to the atleast one feed cavity.